Many of the reasons for choosing to take a trip by bicycle along the Danube River that I discussed in Part 1 of this series are logistical and practical: It's one of the easiest and most comfortable long-distance cycling routes in the world, even if you don't think of yourself as a cyclist.

In Part 2, below, I'll give some additional practical advice for those who are thinking about a trip like this.

And in Part 3, I'll highlight a few specific places to see, do, and stay along or near the river that I found interesting and/or enjoyable, and that you might miss if you weren't looking for them.

The Danube River is the historic route of travel, trade, cultural influence, and conquest between northwestern Europe and southeastern Europe, the Balkans, and Asia. The Danube formed part of the border between the Roman Empire to the south and the Germanic "barbarians" to the north. More recently, the border between the Habsburg (Austro-Hungarian) and Ottoman (Turkish) Empires shifted back and forth across and along the Danube. If you think of the world as defined by a Clash of Civilizations between European Christians and Asian Muslims, than the countries of the Danube are front-line states in that conflict.

The Danube is most often spoken of as flowing from north to south, and for convenience I will use that convention in this article, although the winding course of the river is actually more from west to east.

[The Donauquelle in Donaueschengen.]

The source of the Danube is defined by convention to be either at the ornate Donauquelle fountain in Donaueschengen, in southwestern Germany, or at the confluence of the Breg and Bregach streams a mile or so downstream.

[By coincidence, the Mayor of Donaueschingen, Erik Pauly, dropped by the town square -- on his bicycle, of course -- and gave us a special send-off.]

From there, the Danube crosses the German states of Baden-Württemberg and Bavaria, into Austria at Passau, and across Austria through Linz and Vienna. Just beyond Vienna, the Danube crosses into Slovakia, then flows through Bratislava and along the Slovak-Hungarian border before turning south across the Hungarian plain through Budapest to the Hungarian border with Croatia and Serbia. The Danube forms part of the Croatia-Serbia border, then turns east across Serbia through Belgrade to Romania. Almost a third of the length of the river is along the border of Romania first with Serbia (through the "Iron Gates" in the hills) and then with Bulgaria. Just before reaching the Black Sea, the Danube turns back north into a broad delta that touches the borders of Moldova and the Ukraine.

With respect to conditions for bicycle tourism, the course of the Danube can be divided into three main sections:

The upper Danube across Germany and Austria: The bike route is almost always separated from motor traffic and well marked. All services for cycle tourists including luggage transport and bicycle rental are available. Bicycle tourist traffic is heavy.

Vienna to Budapest: The bike route isn't quite as well marked or in as good condition, but is still largely separated from motorized traffic. Luggage transport and bike rental services are available, although with somewhat fewer choices. Bicycle tourist traffic is still significant but vastly lower. The experience during the day is mainly of riding by yourself, meeting or passing other cyclists only occasionally or at rest stops, rather than constantly being in a stream of cyclists.

The lower Danube below Budapest: Many of the pros and cons in the list in Part 1 of this series, which mainly describes conditions for cycling along the Danube above Budapest, are reversed further downstream. This is the better half of the river's course to ride if you prefer to carry all your own gear, camp rahter than staying in hotels or guest houses, and cover longer distances each day, or if you are willing to put up with sharing roads with motorized traffic for the sake of better pavement, easier route-finding, and fewer unwanted stops.

Almost all of the Danube cycle route is part of the Eurovelo network of transcontinental European cycling routes. Long-distance multi-country bicycle tourism ticks all the buzzword boxes of eligibility for European Union funding: infrastructure for integration of EU member states, promotion of a common pan-European identity, sustainable tourism and transportation, economic development of regions outside the big cities and industrial centers.

From Tuttlingen (a day's ride below Donaueschingen) to the Black Sea, the main through cycling route along the Danube is signed as part of Eurovelo 6. Beware, though: along some stretches of the river, there are alternate routes (sometimes one on a rough unpaved track and one on a paved road shared with motor vehicles, or one on each side of the river), both signed as Eurovelo 6!

Designation as part of a Eurovelo route doesn't imply new construction, standardized infrastructure, or path for cyclists separate from motor vehicles. The Eurovelo routes are more like the Lincoln Highway, the first officially designated and marked through road route across the USA from coast to coast, which followed existing streets and roads of varied character and quality.

In Germany, the most prominent signage on the through Danube cycling route marks it as the "Deutsche Donau" route. In Austria, where the signage is even better than in Germany, the main through cycling route along the Danube across the country from the German border to the Slovak border is signed "R1" (Radweg 1), i.e. Austrian national bicycle highway number 1.

From the Austria-Slovakia border downriver, where development and marking of the bike route has been carried out more recently and primarily under EU rather than national impetus, the primary signage is for the Eurovelo, "EV6", with the EU circle of gold stars on a blue background.

Once you've decided which section of the river you want to ride, you'll have three basic types of route choices to make: which direction to ride (upriver or downriver), whether to ride on the road or the path, and which side of the river to ride on.

Upriver or Downriver? My impression is that at least 98% of the cyclists along the Danube ride downriver from northwest to southeast, as we did. That doesn't mean you should necessarily do the same, but there are reasons, some more valid than others.

Riding in the downriver direction means, at least in theory, riding generally downhill. But the descent of the Danube from its source to sea level is so gradual, averaging about 40 cm per kilometer (two feet per mile) as to be of no real significance. The route is essentially level in either direction.

Supposedly the prevailing winds along the Danube are from northwest to southeast. That's a reason to ride in the downriver direction. We noticed few strong headwinds or tailwinds, but headwinds are always more noticeable than tailwinds. We did have a few days of significant crosswinds. Your mileage may vary, but I wouldn't pick a direction solely on the basis of a hope for favorable winds.

Both the traffic of cyclists and the density of services along the river are greatest in Germany and Austria, and thin out very substantially further downriver. Going downriver, it's easier to start out slowly, and work up to longer stages as you go along.

Where traffic is heavy, the experience of going upriver against the flow of cyclists would be very different from that of being part of the steady current of cyclists headed downstream.

I would hesitate to set out upstream across Austria and/or Germany. I'd be afraid of a head-on collision with a careless group of downstream cyclists riding two or three abreast and taking up the whole width of the path (since they haven't seen any oncoming cyclists for an hour or more) as they round a blind corner.

Further downriver, where traffic is much lighter, the choice is less clear. If you are only riding the lower half of the river, for example you might want to start out from the Black Sea in the spring and work your way north (upriver) as the weather warms up.

The big advantage to traveling upriver, aside from any issues of timing and weather, is that you'll meet cyclists coming toward you at frequent intervals who could give you information about the route ahead of you. That could be good or bad: If you're headed upstream, you might be stopped and questioned more often than you'd like by passing downstream cyclists.

Road or Path? Where there are two alternate bike routes along the Danube, the typical choice is between a route on an unpaved path, and a route on a paved road shared by motorized vehicles. Sometimes one or the other route is shorter, more level, more scenic, goes past some historic or archaeological site or other tourist attraction, or goes through a town with services.

Which Side of the River? Often there are marked cycling routes on both sides of the river. Where the Danube is still a small stream, there are bridges, ferries, or locks and dams on which you can cross the river every few kilometers or miles.

[Typical small seasonal bicycle-and-pedestrian ferry.]

The further downriver you go, the greater the distances between possible crossings. There's no need to agonize over these choices, but make them carefully. Below Budapest, once you pick a side of the river, you are often committed for the next 100 km (60 miles) or more. Below Belgrade, the distances between crossings are even greater. This list of crossings is incomplete -- it doesn't include ferries -- but it's instructive. The BVA and Huber maps mentioned below show all the ferries that carry bicycles, as well as which bridges (almost all) are open to cyclists. Most of the larger bridges have separate bicycle and pedestrian lanes, although the bicycle approach to a big bridge can sometimes be tricky to find without a detailed map.

[Sign showing bicycle approach routes to the next two bridges, and alternate Eurovelo 6 routes on both sides of the Danube.]

The peak season for bicycle travel along the Danube is July and August, especially August. June is a little less busy, with fewer families because many schools in Europe are still in session. May and September are shoulder season, cooler but with much less traffic.

Even southern Europe is pretty far north relative to the USA. Budapest, for example, is at about the same latitude as Seattle. That means that days are much longer in May or June along the Danube than in September or October. If you are trying to avoid the crowds, I'd start a trip down the upper Danube in May.

All else being equal, I'd avoid peak season almost anywhere. But riding along the busiest stretches of the Danube in June and July, we had a pleasantly social experience, not one that felt overly crowded. Perhaps it would have been different in August, but we never had to go too far to find lodging, even without reservations, and prices were often at least somewhat negotiable.

It rarely gets too hot in Germany and Austria, but typical daytime temperatures along the Danube below Budapest in July and August can be uncomfortable. For a bike trip along the lower Danube, consider starting from the Black Sea in May, and heading north up the river, or heading south from Budapest in September.

There are several competing German or German-English bilingual sets of large-scale strip maps with turn-by-turn directions and details of sites and services along the Danube cycle route. Spiral bound and printed on waterproof card stock, they are intended to be carried in or on top of your handlebar bag.

I think the turn-by-turn directions are overkill, and the volume and weight of any of these map sets (the most popular Bikeline maps are in five volumes, each the size of a large paperback book) or any of the Danube cycling guidebooks with turn-by-turn directions is more than I would want to carry.

I recommend the BVA (upper Danube) and Huber (lower Danube) map sets. At a scale of 1:100,000 (1 cm = 1 km, or 1 inch = 1.5 miles), they are compact enough to carry but still show almost every turn except on the smallest city streets. They give enough detail of surface conditions (paved, good unpaved, bad unpaved), major hills, and amounts of motorized traffic (none, light, moderate or heavy), and all bridges or ferries open to cyclists to make informed choices between sides of the river or other alternate routes. Unlike larger-scale maps that show only the riverside route, they show out to about 15 km (10 miles) on either side of the river, which is helpful if you are considering any side trips or detours. The sets for the upper and lower river are from different publishers but at the same scale and in the same format. (The only major difference is that the Huber maps are printed on significantly less water-resistant paper.) Being more compact, these maps are favored by cyclists travelling longer distances along the river:

[These two sets of maps together cover the entire course of the Danube.]

The BVA and Huber map sets are usually available at the Freytag and Berndt map and travel stores (some of the world's best) in Vienna, Regensburg, and Nuremburg, and sometimes at Stanfords in London. But they are sometimes out of stock, and not easy to find in other cities and towns along the Danube. I would order them by mail in advance, if possible.

Where the main cycle route followed a different course than was shown on these maps or on GPX tracks recorded by earlier riders, or where the surface conditions were different than shown on these maps, it was generally because a previously unpaved dike or path had been paved, or a new cycle path separate from the motor vehicle road had been constructed. Conditions were almost never significantly worse than shown on these maps.

[Pouring concrete on the Danube bike path through a steep ravine in a national park in Serbia. If there were any warning signs that the path was blocked ahead, they weren't in English! We had to drag our bicycles through the undergrowth past the paving crew, then carry our bikes across a section of mats of rebar laid out as a base for the new concrete, before we got back to a place where the path was rideable.]

The one infamous exception, as of 2017, is a stretch just south of Budapest where a local farmer plowed up about 5 km (3 miles) of the path, probably with a disc harrow, to render it unrideable. Eurovelo 6 signs direct cyclists onto a dike through farmland between the east bank of the Danube and the towns of Tass and Szalkszentmarton. At the junction with the paved road, the gravel road along the top of the dike looks rough but passable. The Eurovelo is clearly signed as continuing onto the dike. But a kilometer or so down the dike, cyclists are forced either to turn back, cursing, or to stumble on through deep soft dirt, carrying their bicycles and cursing even more.

If you follow the main paved motor vehicle road for about 15 km (10 miles) through Tass between Domsod and Szalkszentmarton, you'll avoid the plowed-up section of dike. This was one of our least pleasant days of riding -- difficult route finding, moderately unpleasant traffic, and ugly industrial scenery in the southern suburbs of Budapest -- but fortunately we had been forewarned about this plowed section of the path weeks earlier and hundreds of miles downriver by some cyclists we passed who were headed in the opposite direction. What mystified us is that this situation has reportedly prevailed for several years without either the dike being repaired or the signs being modified to direct cyclists around the unrideable section.

Cycling is a well-recognized and often the dominant form of tourism in many towns along the Danube, and local and regional tourist offices produce a variety of literature advertising cycle tourism. Unfortunately, most of this free literature is long on promotional photos and puffery, and short on practical information. The German state of Bavaria is an exception: There's not only an exceptional network of signed regional cycling routes, but an excellent free Bayernnetz für Radler cycling map of the state that's worth picking up if you are considering a detour away from the Danube or travel by bicycle elsewhere in Bavaria.

Getting a local SIM card isn't a very good strategy if you will be spending short periods of time in many different countries.

If you live in the USA, the best phone deal by far for international travel is to get an account with T-Mobile USA. T-Mobile USA is the U.S. subsidiary of Deutsche Telekom, the German national phone company, and has leveraged Deutsche Telekom's roaming agreements to offer much cheaper international roaming than any other U.S.-based cellphone carrier. Roaming in most of Europe with a T-Mobile USA phone number and account, voice calls are US$0.20 per minute and unlimited international roaming data and SMS (text message) service is included in your regular monthly bill.

Once it was properly set up, I've had no problem using my T-Mobile USA phone number and account while outside the USA for two months at a stretch. Three months or more and T-Mobile USA says they might suspend your service until you get back to the USA, although they might not.

Having a working cellphone is useful, especially for calling ahead to check availability and prices for lodging, but not essential. You can use a smartphone without a data or voice service plan as a GPS and navigation aid with offline maps, and make voice calls to landlines and cellphones using VoIP apps over WiFi. WiFi is available in many but not all accommodations, including almost all informal homestays but not all local inns.

Cellular coverage along the Danube is good but not perfect. There were stretches of the river with no signal, especially in some of the narrow gorges and wide areas of wetlands and national parks. You can't rely on online maps or a real-time cellular data connection for route-finding.

I don't know of any digital maps that give good information about road surfaces and traffic volumes, or that are as useful for choosing between alternate routes as the paper maps described above. Note that because of German privacy law, Google does not show "Street View" in Germany.

But digital maps are more useful for following the twists and turns of a complicated route, finding precise addresses, or finding your way back to the path if you've made a wrong turn.

Many digital maps show only or primarily those roads open to motorized vehicles. The most comprehensive, accurate, and up-to-date (although far from perfect by any of those measures) digital maps for bicycle travel, especially in areas with extensive networks of dedicated bicycle and/or pedestrian paths, are the crowd-sourced "OpenCycleMaps". You can view them on the Web at OpenCycleMap.org or, more usefully while you are travelling, by choosing the "Cycling" view in the OsmAnd app for Android or any of the other OSM client apps.

(A tip for Android users: Open Street Maps and OsmAnd are free and open source. But if you download them through the Google Play Store, you have to pay extra for the OsmAnd hillshade plugin to show slopes and contours. If you enable the "F-Droid Archive" repository, you can download the hillshade plugin as well as the rest of the OSM app and offline maps hrough F-Droid for free.)

It's easier to keep track of where you are relative to the main Danube cycle route if you download a GPX track of the route and import it into OsmAnd or your navigation app. You can download GPX tracks from the OpenStreetmap wiki page for Eurovelo 6, from RideWithGPS.com (sign up for a free account, then search for rides tagged "Eurovelo 6"), or from BiRoTo.eu ("Bicycle Routes and Tours Europe"). Keep in mind, however, that any GPX track you download probably shows the route of some specific rider who recorded the route of their own trip. They may have deviated from the posted route or chosen different alternatives, and what is signed as the "main" route of the Eurovelo changes a little every year with new construction.

Because accommodation providers can add their own listings, OSM shows substantially more of the available lodging (although not all, and not reliably) than any other Web site, app, or printed directory. It's especially useful for finding informal homestays in between towns. Just don't count on it unless you've called ahead to verify that lodging exists and is available.

The best source for stories by other bicycle travellers along the Danube -- as for bicycle travelogues from almost anywhere else in the world -- is CrazyGuyOnABike.com. Despite the name, it includes travel diaries by men and women, solo travelers, couples, families, and groups of all sorts. Search for trip journals mentioning "Danube" or the name of any of the towns along the portion of the route you plan to ride. As you read these stories, bear in mind that cycle tourism along the Danube is not only very mainstream but very diverse. Your trip won't necessarily be, and certainly doesn't have to be, quite like anyone else's trip along the same river.

There's a good official Web site and app for bike routes throughout Bavaria, although I found the paper map more useful.

Bett+Bike is a certification scheme for "cyclist-friendly" accommodations run by the German national cycle touring advocacy organization, ADFC. The app and Web site list lodgings in Germany and to a lesser extent Austria and other neighboring countries. All Bett+Bike approved hotels and guesthouses provide secure indoor bike storage and full breakfast.

The Danube Austria Web site produced by a consortium of local and regional government tourist promotion bureaus includes online route maps, listings of (some) accommodations and bike tour operators, and notes on sights along the route across Austria.

There are several Eurovelo 6 and Danube travel overview Web sites and apps, but most of them either offer too high-level an overview to be of much practical use once you are along the river, focus exclusively on one or another sub-section of the route, or are mainly advertisements for tour operators.

Any knowledge of German is helpful, but it's definitely not essential.

The most heavily-touristed portion of the Danube is the upper third of its course, through Germany and Austria. Further downriver, German was the language of rule and of higher education under the Habsburg (Austro-Hungarian) Empire until World War I, and again under the Third Reich during World War II. There are minority populations of native or bilingual German speakers in all the countries further down the Danube. German is an important regional language of trade and industry, not just tourism: Since the fall of the Iron Curtain in 1989, many German companies have invested in factories in Eastern Europe to take advantage of cheaper labor, the way U.S. companies have invested in "maquiladoras" in Mexico.

Most of the tourists along the Danube are German speakers, and the common language of tourism along the Danube is German, not English. Even in places where German isn't the first local language, most of the hand-lettered signs along the path advertising informal homestays read "Zimmer Frei", not "Room For Rent". Even a few key words of tourist pidgin German are helpful. "Belegt" means "No Vacancy", for example. Many people in countries further downriver, including staff in hotels, restaurants, and shops, speak a little English, or a little German, but not necessarily both. Similarly, restaurant menus are often bilingual in the local language and either German or English, less often (although not infrequently) trilingual.

But you can get by with just English and a little sign language. We had no trouble staying at hotels and "Zimmer" where none of the staff and none of the other guests (if there were other guests) spoke any English. In a pinch, you can usually find a fellow traveller who speaks enough English to translate for you.

There are ATMs in every big town, but not necessarily in every village. Some informal homestays only accept payment in cash. So even in the Euro zone it's best to keep a few days cash reserve.

Germany, Austria, and Slovakia use the Euro. Every country further down the Danube uses its own currency. We had no trouble getting local currency from ATMs in every country along the Danube except Serbia. We changed cash Euros for Serbian Dinars at banks or moneychangers, and were able to use US-issued credit cards for purchases in Serbia even where the banks and ATMs wouldn't let us make cash withdrawals. Prices for lodging are often quoted in Euros, and even if the price is quoted in local currency you can often get a better price if you offer to pay cash in Euros. So if you're headed south, stock up on Euros before you leave Slovakia. Try to avoid having too much of any currency except Euros left over, as moneychangers can be hard to find.

I'm not a fan of German food, but we ate better than I had expected. Restaurant food in Germany was carefully prepared with quality ingredients -- it was just a bit bland for my taste. Austrian food was similar but generally better than German. If you want something spicier, "ethnic" food in Germany and Austria, as in much of the rest of Northern Europe, is more or less synonymous with Turkish or Balkan cuisine -- which I love. It's spicier, cheaper, and more varied, and Turkish or Balkan restaurants and snack ("Imbiss") takeout stands are typically open much longer hours than their "European" competitors. The same is true for grocery stores and many other services. Standard German and Austrian businesses keep short hours, but you can often find shops open at other times in the ethnic Turkish and immigrant neighborhoods found in every German or Austrian town of any size.

(Residents of the "Turkish" quarter of a German or Austrian city or town aren't necessarily Turkish by citizenship or ethnic identity. For starters, many of them are Kurdish, not Turkish. And many are second- or third-generation residents of Germany or Austria, natively fluent or bilingual in German, who identify themselves as Germans. Hyphenated ethnic-national terms like "Turkish-German", common in the USA, are much less often used in Germany or Austria. Whether or not they intend it as a slur, many northern Europeans refer to all Muslims as "Turks", regardless of their actual citizenship or ethnicity, the same way many people in Latin America refer to anyone of Asian ancestry as a "Chino", even if they are a second- or third-generation Japanese-Brazilian or Japanese-Peruvian.)

The food gets cheaper and more interesting as you get further down the Danube. Hungary in particular is a first-class foodie destination: one of those smallish countries with an unusually distinctive and diverse national cuisine that's hard to find outside the country. Enjoy it while you are there! We found pleasant culinary surprises in Slovakia and Croatia, where we had little idea what to expect. Serbian food was great.

Bavaria is better known for beer than wine, but there are wineries along the banks of the Danube for much of its length.

There are well-marked public toilets in most villages along the Danube bike path. Most bars and cafés will let you use their toilets even if you're not a customer, although it's polite to buy something if you use the facilities.

The Green Party has been trying to get a law passed in Germany, similar to the one their counterparts got enacted in France a few years ago, requiring restaurants to serve free tap water on request. But that isn't yet the law in Germany, and most restaurants in Germany refuse to serve tap water. If you ask for water, you'll get a choice of still bottled water or fizzy bottled water. The expectation that every diner will pay for something to drink is factored into their price structure. If you ask for tap water, you'll be regarded as someone who's trying to cheat them out of their fair profit on the meal.

On the other hand, if you order something -- anything -- to drink with your meal, or make some other purchase, the wait staff will generally be happy to fill your water bottles for you. And many beer gardens and restaurants along the bike path provide an outdoor tap for cyclists to use to fill their water bottles.

It's also acceptable for a cyclist to go into a bar or café and ask to have his or her water bottles filled. Just don't ask for tap water with your meal in any sort of restaurant.

We had no problems with ill-behaved dogs or motorists. We heard conflicting rumors about Romanian mastiffs and Bulgarian truck-drivers, but we didn't get that far down the river.

Intermittently throughout July, sometimes for hours on end, we found ourselves riding through clouds of tiny gnats. They didn't seem to sting or bite at all, but it was sometimes hard to avoid inhaling them, and by the ends of some days our arms and legs were speckled with minute black dots of dead bugs. Nobody was able to tell us what sort of insect these were.

We encountered hardly any mosquitos or other biting flies or insects -- somewhat surprisingly, since we were often riding along canals, marshes, and slow-moving pools of water.

A larger percentage of the population smokes in Germany than in the USA, but German smokers are generally very considerate of non-smokers. Non-smoking signs and rules are scrupulously observed, without apparent resentment. There may not be any designated non-smoking rooms in a village inn, but the rooms had usually been well enough cleaned that we didn't have a problem.

There's a bike shop in every sizeable town along the main Eurovelo route in Germany and Austria. Further downriver, you can find bike shops in cities and larger towns, although those get further apart. Where bicycles are used for local transportation, such as in rural Hungary, some garages that work on cars and motorcycles also service bicycles, and small-town hardware stores sell some basic bicycle parts and accessories.

It's common for a bike shop or hardware store to have an after-hours bicycle tube vending machine on the wall outside the entrance. Look for a square metal box on the wall about a meter (3') square in Continental yellow or Schwalbe blue. Along the Eurovelo, a typical tube vending machine is stocked with tubes in several diameters and widths, and all three major types of valves: Presta, Shrader, and Woods/Dunlop. Check the descriptions and illustrations carefully to make sure you are getting a tube that will fit your rim and that you can inflate with your pump.

You never know what type of valve or pump you'll find, so bring Presta-Shrader adapters (and know how to use them). Metric tire pressures are commonly specified in "bar", or occasionally in kPa. One bar (one atmosphere) is 100 kPa or approximately 15 psi.

The German national organization of cyclists, ADFC, has German-English and English-German glossaries of bicycle terminolgy on their Web site. In German, a bicycle is a Fahrrad, a bicycle path or route is a Radweg, and a bicyclist is a Radler. A "Radler" is also a drink, supposedly popularized by bicyclists, consisting of a mix of half beer and half lemonade.

There's such a wide variety of bikes being ridden along the Danube that no shop can possibly have parts for all of them in stock. From Slovakia onward, the most readily available tubes, tires, and other components may be locally made and of lower quality than the best Western European or Japanese models. But if something breaks, and no replacement is available locally, a shop can order it for you, or you can order it, and have it delivered from Germany or France (the centers of Western European bicycle component sales and distribution) in a couple of days. Mail ordering might be a bit slower and more expensive in Serbia, the only country along the Danube that isn't in the EU, but should still be possible.

A full discussion of the nuances of variation between the local cultures of cycling in different countries along the Danube, much less throughout Europe, would be an interesting project but far beyond the scope of this essay.

However, to the extent that local attitudes toward cycle tourists are shaped by local attitudes toward cycling in general and the role of cycling in local communities, it's worth noting that these vary considerably from country to country:

Germany: Germany is the unnoticed heartland of bicycle touring. Not quite as large a percentage of the population uses bicycles for everyday transportation in Germany as in the Netherlands or Denmark. But the bicycles most commonly used for everyday transportation in Germany are better suited for touring. Dutch bikes are too heavy to ride any distance, or on hills.

Standard German commuter bikes have gears for hills, fenders for rain, racks and baskets for luggage, and -- by law if they are ridden after dark -- generator-powered lights. Much of the popularity of bike touring in Germany stems from the fact that so many Germans already have suitable touring bikes, without needing to make any additional investment in gear. And there's a comfort factor in travelling on the same bike you ride every day around home.

Austria: Cycling for transportation isn't quite as common in Austria as in Germany, but that's offset by a national emphasis on fitness and outdoor recreation.

Slovakia: We rode into Slovakia on the same day that Slovak national sporting hero Peter Sagan won a stage of the Tour de France. The next day Sagan was expelled from the Tour, following a collision with the race leader, in a much-disputed decision by the race referees. Not surprisingly, we saw a high percentage of riders in racing kit on the bike paths on those days.

Hungary: Hungary has strong traditions of bike racing and transportation bicycling. Hungary under Communism was never wealthy enough to abandon bicycles entirely for private cars. We saw farmers cycling to work in the fields, people cycling home with their groceries in small towns, and recreational riders on lovingly-maintained old steel-framed bikes. All this means that Hungarian motorists are prepared to encounter cyclists at any time on all sorts of roads, even in the countryside.

Croatia and Serbia: In Serbia and Croatia, unlike any of the countries further upriver, cycle tourists are assumed to be foreigners from wealthier countries, not locals. Relatively few foreign tourists come to Serbia or to inland Croatia, but most of those who do come by bicycle. Both Croatians and Serbians see themselves as misunderstood (in the case of Croatia overlooked, and in the case of Serbia demonized) in the eyes of the world, and are eager to use foreign tourists to explain themselves to the world. Once you establish that you are willing to listen, and put aside any pre-judgments, the welcome couldn't be warmer.

Romania and Bulgaria: We didn't get this far, but riders coming upriver told us that horse-drawn carts and wagons were common on rural roads in Romania and Bulgaria. Motorists looking out for these or other slow-moving vehicles and agricultural implements are also more likely to be alert enough to notice and avoid hitting slow-moving cyclists.

For any of the stages between Donaueschengen and Budapest, you can rent a bike or e-bike. If you plan to go any further downriver, or you don't like the bikes available from rental agencies, you'll have to bring your own bike. We talked with several experienced cyclists who had rented bikes for the Danube to avoid the cost and hassle of shipping their own. They all said the rental bikes were adequate, but a bit heavy and offered in a limited number of sizes that weren't necessarily a perfect fit. If you rent a bike, consider bringing your own saddle and perhaps pedals if you don't want to take potluck.

The nearest major airport to the source of the Danube is Zurich (airport code ZRH), just across the border in Switzerland. Between Zurich and Donaueschingen, you could ride your bicycle -- I did it in 2014 -- but it's an arduous climb over the ridge that separates the Rhine and Danube drainages. Cyclists aren't allowed on the road used by motor vehicles, but have to take a steeper and higher path through the forest that in places is really only suitable for mountain bikes, not loaded touring bicycles. The alternatives are to fly into Munich (more distant but sometimes easier) or to take your bike on local trains between Zurich and Donaueschingen, as discussed in the next section.

You might find cheaper or more direct flights to Munich (MUC), which is a larger airline hub than Zurich. Munich is on a tributary of the Danube, and there are relatively level bike routes from Munich to the Danube. If you want to start at the source of Danube, there are local trains between Munich and Donaueschingen or Munich and many other points along the Danube in Germany.

The closest airport to the Danube delta is at Constanta, Romania (CND), on the Black Sea at the mouth of the Danube Canal. Turkish Airlines has connections to and from Constanta via Istanbul, with surprisingly inexpensive through fares to and from everywhere Turkish Airlines flies in the USA.

The next closest airport to the mouth of the Danube is at Varna (VAR), on the Black Sea coast of Bulgaria. Austrian Airlines (one of the subsidiaries of Lufthansa) has connections to and from Varna via Vienna. Further away but with more choices of flights, many international airlines serve Bucharest, Romania (OTP) or, progressively further away, Sofia, Bulgaria (SOF), or Thessaloniki, Greece (SKG).

Almost all airlines will transport bicycles as checked baggage, for a price, if they are properly packed. Each airline has its own rules for how much (if anything) they charge, and whether and if so how they require bicycles to be packed for shipping. The written rules are often ambiguous and allow considerable discretion to airline check-in staff. Even when the written rules seem to be clear, they may not correspond to actual practice.

You can never be sure in advance how much you'll have to pay, or whether your bicycle will be accepted by the airline. The safest thing, if it's possible, is to go to the airport before you buy your ticket or pack your bicycle, and talk to the same people who will actually be checking you and your bicycle in.

Most (although not all) airlines require bicycles to be boxed, and charge a fee for each boxed bicycle as an oversized item. The most common fee for checking a bicycle on a transatlantic flight is US$150 per bicycle in each direction, US$300 round trip.

You can usually find a bike shop to give you a box for free, but it's a fair amount of work (a couple of hours of labor charges from a bike shop) to box or unbox a bike, especially a touring bike with fenders, racks, lights, etc.

If you want to get your own bike from the USA to and from the Danube, two airlines stand out from the crowd in different ways:

Lufthansa transports unboxed bicycles between most airports they serve, including Bucharest but not including Varna or other airports served only by subsidiaries. Wheel your bike up to the check-in counter, hand it over, and it will be wheeled back out to you at the oversize baggage counter at your destination.

[Checking in our unboxed bikes at the Lufthansa counter at SFO airport. We taped foam tubing (pipe insulation) over some of the frame tubes, but that wasn't required.]

In 2014, my partner and I flew on Lufthansa from San Francisco to Zurich, and bicycled out of the airport to our hotel the night we arrived.

[As we were changing planes in Munich, we saw our bikes being wheeled onto our connecting flight. Look just below the fuselage and you can see the front wheel of my bicycle near the lip of the platform at the top of the loading ramp.]

The down side of this convenience is that Lufthansa charges US$150 per bicycle on top of airfares that are rarely the cheapest.

Within contiguous continental Europe, it's generally easier to transport a bike by train, bus, and/or ferry than by plane. Lufthansa transports unboxed bikes within Europe as well as on its long-haul routes, but one-way trickets on Lufthansa for flights within Europe are often much more expensive. Another airline that carries unboxed bikes within Europe, generally much more cheaply than Lufthansa, is Air Baltic, a low-fare airline based in Riga, Latvia. Air Baltic's routes extend across Europe and the Balkans, south to the Mediterranean, and east to Central Asia, including several airports in the Danube region. Air Baltic carried our bikes, unboxed and with no hassles, from Helsinki via Riga to Brussels, for only EUR35 per bike.

Turkish Airlines is practically the only airline that flies to Constanta, and generally has the lowest fares between the USA and most places along the Danube with international air service. Turkish Airlines allows two checked bags per person on all tickets between the USA and Europe, where Lufthansa and most other airlines allow at most one. Turkish Airlines' change fees are less than many other airlines, which makes them a good choice if you aren't sure how far up or down the Danube you might get, and might change when or where you fly home from. Unfortunately, I haven't been able to get a straight answer as to whether Turkish Airlines requires bicycles to be boxed, or whether they will count a boxed bicycle as one of your two free pieces of checked luggage. I suspect both answers depend on the whims of check-in staff at the airport. I've taken a bicycle with me to Europe and back on Turkish Airlines, but it was a folding bike that fits into a bag within the size limits for a standard piece of luggage.

You don't have to return to your starting point to fly home, and doing so is unlikely to save you money. Almost all trans-Atlantic airfares allow "open jaw" tickets, flying into one city and back from a different one, for the average of the round-trip airfares (the sum of the half-roundtrip prices) to the two points. As of late 2017, by far the most direct and cheapest air tickets from the USA for a bike trip the length of the Danube would be open-jaw tickets on Turkish Airlines to Zurich and home from Constanta, or vice versa. But prices, routes, and baggage allowances and fees can change at any time.

There are rail lines intersecting the course of the Danube at frequent intervals from its source to Budapest. You can use trains to get yourself and your bike to and from the start and end of your ride, as your "sag wagon", or for side trips.

Below Budapest there's no railroad along the Danube, and it's often a considerable distance from the river to any train station with passenger service. I've been told consistently that bus service in Bulgaria and Romania is better than train service, but it's not clear how easy it would be to take your bike on a bus. Couplers might make the difference.

For train schedules and (incomplete and not necessarily reliable) information about which trains allow unbagged bicycles, see the Web sites and apps of the Deutsche Bahn (also useful for schedules although not fares in neighboring countries) and the Trainline and Loco2 online travel agencies.

You can bring bikes on most European and Balkan trains, but not without complications. Bikes are dealt with differently by different railroads and on different types of trains, generally in one of three ways:

Most local trains carry bicycles in designated cars. Check the timetable to see which trains allow bicycles, and look for bicycle symbols next to the doors when the train arrives. You might have to buy a special day ticket for your bicycle, but for transport on local trains these usually cost only 5 or 10 Euros. You might have to lift your bike up and down a a couple of high steps to get it on and off the train, and if the car is crowded you might have to pull your panniers off the bike, but you don't have to bag, box, or disassemble your bike -- just wheel it on. There might be hooks to hang bikes, or a railing along the wall of the car. Bring a bungy cord to secure your bike.

High-speed trains including the ICE (Germany and neighboring countries), TGV (France), and Thalys (France, Belgium, Netherlands, and Germany) allow bicycles onboard only if they are bagged, in which case they are treated as oversized, but permissible, hand luggage. High-speed trains subject to this rule are the only trains on a growing number of routes, especially on international routes.

The exception for bagged bicycles is explicit in France but unwritten in Germany, the Netherlands, and Belgium. If you ask, you will probably be told that no bicycles, or only folding bicycles, are allowed on ICE or Thalys trains. This is not true. In practice, I've taken my touring bike, bagged, on ICE trains, I've seen many bagged bicycles on the Thalys and TGV, and I've never heard of anyone not being allowed to bring a bagged bicycle onto an ICE or any other European high-speed train (or onto a high-speed train in East Asia, where the same rules generally apply).

The type of bag you want is what's called an "housse de transport vélo" in French or a "rinko" bag in Japanese. It's often just called an "housse" (the intial "h" in French is silent), but be careful: in other contexts the word "housse" in French can refer to several types of sack or cover, including a condom! I don't know the word for this type of bicycle bag in German. You can buy an housse or rinko bag at most bike shops or sporting goods stores in France or Japan, but some are heavier and bulkier than others, and they are hard to find in Germany, Austria, or most other countries. If you might be taking your bike on trains, get one before your trip.

Montbell sells several sizes of rinko bags, but only in Japan or by mail order from Japan -- none of them are sold in the Montbell stores in the USA. This quick carry model is larger and intended to allow you to fit a racing bike in the bag by removing only the front wheel, leaving the rear wheel on the frame. It will probably take some extra disassembly to fit a touring bike with fenders and/or a rack. This model is smaller and designed to fit a racing bike with both wheels removed from the frame, but it also turns out to be perfectly sized to fit the two separated halves of a bike with couplers, even a large touring bike with fenders and front and rear racks. It's lighter and less expensive than anything else I've seen for the purpose, and folds down to the size of a water bottle when you aren't using it.

The point of an housse or rinko bag isn't to protect the bike, or to hold its weight (normally an housse comes with a shoulder strap that attaches to the bicycle frame and extends out through openings in the bag) but to protect the train, other passengers, and their luggage from bicycle grease and mud.

High-speed trains were designed with minimal space for carry-on luggage, on the assumption that they would be used mainly by business travellers on day trips. As high-speed rail networks have expanded across Europe, it's become apparent that more luggage space is needed. Thanks to lobbying by French and German cycling associations, the next generation of ICE and TGV cars will have more larger spaces for bikes and other luggage. But it will take many years for the existing cars to be replaced or retrofitted. In the meantime, look for space to fit your bagged bike between rows of seatbacks, at the end of the car, leaning against the luggage rack, or wherever the conductor directs you. Be considerate of other passengers, and for safety's sake don't block passageways.

Older Soviet-style (often East German) or Yugoslav railroad cars used in Serbia, Bulgaria, and Romania may have no space designed or officially designated for bicycles. In practice, bicycles are carried wherever they fit on trains like this, for a fee/bribe negotiated with the conductor. At the train station in Belgrade, we were told to expect to pay EUR5-10 each (the fee/bribe was quoted in Euros, not Serbian Dinars) to bring our bikes with us on the international "express" to Sofia. We decided not to buy tickets for that train, after we saw what it looked like: two chair cars with sealed windows but no air conditioning for an all-day ride in 35+°C / 95+°F weather, with no sleeping compartments, dining car, or food service.

"The Danube: A Journey Upriver from the Black Sea to the Black Forest", by Nick Thorpe (2013, Yale University Press, ISBN 9780300181654): A thoughtful travelogue by a Budapest-based BBC correspondent. Thorpe originally intended to make much of his journey by bicycle, but had to abandon that plan after he was hit by car and badly injured on a street near his home in the southern suburbs of Budapest. (Along one of the sections of our route where we found the motor vehicle traffic most unpleasant, as noted above.) Thorpe completed his journey by car, but using the Bikeline cycling maps to find roads following the river as closely as possible. Aside from its emphasis on the lower river, which gets short shrift in most Danubian literature, Thorpe's book is especially interesting for its treatment of modern issues of water pollution, fisheries, land use, and the environmental impact of the wars in the former Yugoslavia. Very highly recommended but out of print in the U.S. and surprisingly hard to find in any of the towns along the Danube. I ordered a second-hand copy from a bookstore in the U.K., and had it mailed to the one hotel I booked in advance at the start of my trip.

"Through the Embers of Chaos: Balkan Journeys", by Dervla Murphy, 2002, John Murray, ISBN 978-0719562327: Dervla Murphy is certainly the finest bicycle travel writer alive, and among the finest travel writers regardless of their mode of transport. It's worth reading whatever she has written about anywhere one plans to travel, the more so if you plan to travel by bicycle. Relatively little of this book takes place along the Danube -- she took the hardest high roads and tracks across the mountains, not the easy route of the river -- but she provides perspectives on the wars in the former Yugoslavia that mainstream media won't. We decided to take a trip along the Danube before we had thought much about the fact that the river passes through key battlefields of these recent wars. If this books assumes you already know more than you do about the role of the USA and NATO in these wars, or makes you realize that you ought to learn more before you visit places and meet people who were bombed not so long ago by a government claiming to act in your name, that's probably a good thing.

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"Liberty of movement is an indispensable condition for the free development of a person." (United Nations Human Rights Committee)